Some men see them as a status symbol, but research has found mobile phones could be destroying that other badge of masculinity - fertility. Men who spent hours talking on their mobile phone had significantly lower sperm counts than usual, according to a study presented at the American Society for Reproductive Medicine conference.

Ashok Agarwal, from the Cleveland Clinic in Ohio in the US, examined 364 male fertility patients and found heavy mobile phone use led to men producing fewer and poorer-quality sperm. "There was a significant decrease in the most important measures of sperm health," Dr Agarwal said. "People use mobile phones without thinking what the consequences may be. It's just like using a toothbrush - but mobiles could be having a devastating effect on fertility."

He found that sperm count, viability, motility and shape declined as mobile phone usage increased. Within the study group, those men who did not use mobile phones were found to have average sperm counts of 86 million per millilitre. This dropped to 69 million per millilitre for men with mobile phones who used them less than two hours a day, 59 million per millilitre for usage of two to four hours and 50million per millilitre for more than four hours a day. A normal sperm count is considered to be anything from 20 million per millilitre to 150 million per millilitre.

"The effect of mobile phones on sperm may be due to the electromagnetic radiation the devices emit or to the heat theygenerate," Dr Agarwal said yesterday.